COMBINATION OF ANAEROBIC-DIGESTION AND DENITRIFICATION IN A HYBRID UPFLOW ANAEROBIC FILTER INTEGRATED IN A NUTRIENT REMOVAL TREATMENT-PLANT

A new nutrient removal plant configuration was designed and tested in pilot-scale for the treatment of piggery wastewater. The core of the p rocess is represented by a Hybrid Upflow Anaerobic Filter where both a naerobic digestion and denitrification takes place. The pre-screened p iggery wastewater is fed to the mesophilic anaerobic reactor. In the b ottom of the sludge bed, anaerobic digestion and sulfate reduction are the prevalent processes. In the upper filter zone, a stream of nitrif ied clarified effluent is recycled and nitrates are denitrified utiliz ing the remaining available carbon and sulfides as electron donors. Th e anaerobic reactor should be slightly overloaded in order to provide VFAs for denitrification. The effluent of the anaerobic reactor is fed to the following P-removal stage, which is composed of a sludge pre-d enitrification step, an anaerobic P-release step, an aerobic nitrifica tion tank and a final settler. The pilot-plant treated 5 m(3) d(-1) of pre-screened piggery wastewater. The anaerobic digester (volume 15 m( 3)) demonstrated it was to couple anaerobic digestion and denitrificat ion. The overall plant removal efficiency was around 96% for COD, 92% for nitrogen and 92% for phosphorus. The anaerobic digester contribute d 80% to the overall denitrification capacity.